Principles of RDF

There are two general ways in which to find the relative direction (bearing)
of a transmitter from your current location. One uses signal strength and
a directional aerial. Another uses Doppler Shift. The directional
aerial method is the cheapest. Aerials are often home made and attract
embarrassing, disparaging or admiring comments on their appearance. The
Doppler Shift methods can be used by making a circuit from scratch, from a kit
or by buying one complete.

Other requirements are a magnetic compass (with the ability to use it), a
protractor and maps of the area.